This invention relates to monitoring the temperature of drums used in the dryer sections of machines used to process sheets of paper, textiles, and the like.
Papermaking and textile machines handle continuous sheets of paper or fabric. One of the steps involved in making paper or the processing of textile products is the removal of moisture from the product. The textile or paper materials are typically dried by passing them over the surfaces of a series of cylindrical structures called drums. Because the production rate and the quality of the product are affected by the temperature of the drums, maintaining proper drum temperature is an important aspect of the production process.
One technique for monitoring dryer drum temperatures involves using a handheld infrared temperature sensor gun. Temperature readings can be taken by pointing the sensor gun at an exposed surface of a drum. However, such temperature readings must be taken manually and are strongly influenced by the emissivity of the drum. Because drum emissivity can vary depending on the surface condition of the drum (i.e., whether the drum is painted, rusted from exposure to water, shiny, etc.), temperature readings taken using handheld infrared temperature sensors can be inaccurate.
Another technique for monitoring drum temperatures involves using a handheld rubbing-contact temperature sensor. Rubbing-contact temperature sensors typically have wheeled carriages that are placed in rubbing contact with an exposed surface of the rotating drum. Because rubbing-contact sensors are placed near to the moving surfaces of the papermaking machinery, using such sensors is not without risk to the operator taking the temperature measurement. In addition, typical rubbing-contact sensors are speed rated, so that a given sensor can only be used to make temperature measurements if the drum is rotating below a particular speed.
Still another technique for monitoring drum temperatures involves calculating the drum temperature based on known parameters, such as the pressure of the saturated steam used to heat the interior of the drum, the thickness of the water condensate layer built up on the inner drum surface, the rate of evaporation on the exterior of the drum, the structure of the drum (i.e., whether the drum has any raised surfaces), etc. The results of this type of heat flow analysis tend to be inaccurate, because it is not possible to measure or determine all of the parameters that influence the drum temperature or to precisely gauge the interplay between the various measured parameters and the drum temperature.
It is therefore an object of the present invention to provide improved techniques for monitoring the temperature of the drying drums in machines used to process sheets of paper, textiles, and the like.